WASHINGTON (CNN) -- Bush administration officials used Sunday's talk shows to defend last week's heightened security alerts in three cities and to underscore the administration's focus on terror threats.

"You have to go out and warn. You have a duty to warn," national security adviser Condoleezza Rice said on CNN's "Late Edition."

The decision to raise the alert level to orange, or elevated, for specific buildings in New York City; Newark, New Jersey; and Washington, D.C., has been criticized because it was based at least partly on information three or four years old.

Rice conceded that the surveillance of the buildings by al Qaeda operatives dates to before the attacks of September 11, 2001.

"But the information that there were plots under way that might relate to the pre-election period came from multiple sources, and active multiple sources," Rice said.

"It's inconceivable to me that we would not have informed the Citigroup or the New York Stock Exchange or the World Bank that known terrorists have cased their buildings," she said.

Rice said the Republican National Convention in New York is going to be "as best as we can make it, a very well-protected event, as was the Democratic convention."

The Department of Homeland Security named both conventions national special security events, meaning the Secret Service will coordinate security. The security budget for both events will total $100 million.

Former New York Mayor Rudy Giuliani, who appeared on the same program, predicted that many New Yorkers would leave town during the August 30-September 2 convention, but not necessarily because of heightened security and terror threats.

Many residents left the city during the Democratic convention in 1992 and "let the delegates sort of take over," Giuliani said, noting that vacations and the end of summer would prompt many residents to leave.

"The [security] preparations here in New York are probably the best in the country," Giuliani said. "Life goes on, our politics have to go on. And we can't let these politics stop us."

Giuliani, too, defended the heightened alert, saying he took the warnings "very seriously."

"It's some of the most specific information that we've had, not only about buildings but about method of attack," he said. "I think the warning has helped to make us even more alert."

Retired Gen. Wesley Clark, former NATO supreme commander and one-time candidate for the Democratic presidential nomination, said the Bush administration "did the right thing, but they did it the wrong way."

"When you raise the alert level, you've got to do it in a way that you're explaining and laying out as much as you can about why it is that you're doing it, what you hope to achieve from it," Clark said on "Late Edition."

"The way the information dribbled out over time, it undercut the credibility of the system. That's the last thing we want," he said.

Former White House counterterrorism coordinator Richard Clarke, speaking on ABC's "This Week," said the Bush administration's color-coded warning system is "a laughingstock" among state, local and business officials he has talked to.

"I've talked to a lot of state directors of homeland security, state officials, mayors, heads of big companies, and they all say they don't take it seriously," Clarke said.

"They don't get good information from [Secretary] Tom Ridge and the Homeland Security people. There's very bad communication, very bad messaging."

Clarke said Ridge "is not a good spokesman for this issue. When he says things like 'Here's a warning,' then in the next breath says the president is doing a great job, that just raises suspicions."

White House homeland security adviser Frances Townsend, speaking on CBS's "Face the Nation," said it appeared the data about the financial sectors was part of al Qaeda's plans to disrupt the U.S. election in November.

"While it's not clear if this is the entire pre-election plan, this certainly looks like it was a piece of it," she said.

Townsend also referred to threats against the Capitol building and certain members of Congress, but did not provide details.

The threats were "in the past and as part of this continuing threat stream, and so we shared that with them," Townsend said, referring to members of Congress without naming them.

In a book released earlier this year, "Against All Enemies," Clarke said the Bush administration failed to take terrorism seriously before the attacks of September 11.

He praised recent U.S. intelligence efforts and the arrest of a suspected al Qaeda operative and computer expert in Pakistan, which was followed by other arrests.

"I think we have broken up an element of the [terrorist] plot of attacks against certain buildings in New York City," Clarke said.

He said the week had produced "the best series of leads, leads going to other plots, leads going to other people, international cooperation -- I don't think we've seen this in five years."